Haddam is a town in Middlesex county in Connecticut. It was formed in 1668 from the following town or towns: New London. Haddam is a part of the Haddam probate district and has been since 1830. Middletown/Chatham was/were the previous chronological district or districts. For more information, contact the county at 30 Field Park Dr. P.O. Box 87 Haddam 06438-0087. On the attached map, Middlesex is located at F5.